A conventional drum typically comprises a hollow drum shell having two drum heads, each of which is held in place at opposite ends of the drum shell by head hoops. Conventional drums are usually not tunable except in a very narrow range by adjustment of the head hoop.
An adjustable pitch drum consists of a drum shell having an open end, a drum head pitch changing mechanism, and a supporting structure mounting the pitch changing mechanism to the drum shell. The pitch changing mechanism consists of a threaded rod adjustably threaded to the supporting structure, a drum head clamping hoop mounted coaxially on the rod for rotation thereabout, and a drum head tensioning hoop non-rotatably mounted on the other end of the rod. Rotation of the drum head and its clamping hoop about the rod varies the tension of the drum head on the tensioning hoop, thereby changing the pitch of the drum. Movement of the threaded rod in the supporting structure changes the spacing of the drum head from the drum shell open end, thereby changing the resonance characteristics of the drum assembly. A rototom is a designed adjustable pitch drum made by manufacturers around the world, including Remo, Inc. of California. The rototom is in public use and on sale but its written description may not be readily found in patents or published literature other than a limited amount of advertising literature available from various manufacturers.
FIG. 1 illustrates three rototoms 10A, 10B and 10C mounted in a series on a horizontal bar 22 supported by a stand 20, each facing in the same direction, namely, vertically upward. Each rototom has similar components and thus the following description of rototom 10A applies to rototoms 10B and 10C. As with typical rototoms, rototom 10A has a drum head or membrane 11 (often transparent) with an upper surface on which a drummer makes contact with drum sticks (not shown). The drum head 11 is mounted on a supporting hoop 14 with a threaded shaft 12 extending from an underside of the supporting hoop 14. A rigid multi-legged spider support 16 is secured on a threaded tubular support 18 which rides on the threaded shaft 12. Instead of adjusting each tension rod 19, rotation of the supporting hoop 14 about the shaft 12 in a direction by the drummer causes the threaded tubular support 18 to move upwardly or downwardly on the threaded shaft 12 so as to vary the tensioning force applied by the spider support 16 against the drum head or membrane 11 to tune the same. The rototoms 10A, 10B and 10C are generally linearly aligned on the horizontal support bar 22 with their respective drum heads or membranes 11A, 11B and 11C facing in a generally upward direction so that the drummer can strike the drumheads in a downward direction.